Method for fabricating a rolled product made of 4000 aluminum alloy for tank fabrication

Abstract

Method for fabricating a rolled product made of 4000 aluminum alloy and having a thickness of 0.8 mm to 12.5 mm such that the composition of the rolled product comprises in % by weight: Si: 11.5-12.5; Fe: ≤ 0.6; Cu 0.1-1.0; Mn ≤ 0.3; Mg: 0.3-1.0; Ti 0-0.15; Sr 0.01-0.05; other elements and impurities ≤ 0.05 each, total ≤ 0.15, the remainder being aluminum, comprising the successive steps of homogenization, rolling, solution heat treatment and tempering such that tempering is carried out at a temperature of from 160°C to 180°C for a duration of 3 h to 24 h. The product thus transformed has a yield strength in the the transverse to rolling direction Rp0.2 (TL) of at least 280 MPa, and a Kapp (T-L) value of at least 35 MPa√m.

Description

[0001] DESCRIPTION

[0002] Title: Manufacturing process for a rolled product made of aluminum alloy 4000 for tank manufacturing

[0003] technical field

[0004] The invention relates to the manufacture of a rolled product in aluminium alloy 4000 comprising a Si content greater than 11.5% for the manufacture of tanks, preferably cryogenic liquid storage tanks intended for civil aviation.

[0005] Previous art

[0006] Cryogenic liquid storage tanks consist of three basic elements:

[0007] An internal pressure vessel: The internal pressure vessel contains the cryogenic liquid and must be made of a material that can withstand extremely low temperatures without cracking or degrading. High-strength aluminum alloys are lightweight and resistant to these conditions, making them an ideal material for these vessels, especially in weight-critical applications.

[0008] Insulation: The space between the inner and outer tanks contains up to several centimeters of insulating material held under vacuum. The vacuum and insulating material in cryogenic tanks help reduce heat transfer and maintain cryogenic liquids at extremely low temperatures.

[0009] An external tank: Tanks used for long-term storage of cryogenic liquids, for example in a commercial aircraft, have an external tank which is not normally exposed to cryogenic temperatures.

[0010] The present invention relates preferably to the internal pressurized tank, but can also be applied to the external tank.

[0011] Cryogenic liquids are gases that liquefy at low temperatures. For example, hydrogen is liquid at -253 °C.

[0012] The use of aluminum alloys for the manufacture of cryogenic liquid storage tanks is known in the space industry.

[0013] The AA2219 alloy was registered in the 1950s by the Aluminium Association and is widely used in space applications. It is distinguished by the addition of vanadium [0.05 - 0.15], titanium [0.02 - 0.10], and zirconium [0.10 - 0.25], elements which promote fine grain formation in fusion welds, thus reducing the risk of hot cracking.

[0014] More recently, Al-Cu-Li alloys have been used for space applications. These alloys offer a 5% reduction in density compared to the AA2219 alloy and improved properties, allowing for structures with mass reductions of 4% to 33%. Among the Al-Cu-Li alloys currently used for hydrogen storage tanks, AA2195 was used on the US Space Shuttle.

[0015] US5455003 discloses a process for producing aluminum-copper-lithium alloys that exhibit improved strength and toughness at cryogenic temperatures. These enhanced cryogenic properties are achieved by controlling the alloy composition and processing parameters such as the amount of work hardening and artificial aging. The ability to achieve strength and fracture toughness substantially equal to or greater at cryogenic temperatures than at ambient temperature allows the alloys to be used in cryogenic tanks for space launch vehicles and similar applications.

[0016] Al-Mg-Si alloys, from the 6XXX series, are also being considered for liquid hydrogen storage. Oda et al. ("Loading frequency effect on fatigue crack growth rate in low-pressure hydrogen gas environment in the case of 6061-T6 aluminum alloy," A Hen / Transactions of the Japan Society of Mechanical Engineers, Part A, 2009, vol. 75, no. 760, pp. 1746-1753) highlight the advantages of using AA6061 alloy as a storage tank. The 6XXX alloys offer a low density (2.69–2.71 g / cm³) compared to AA2219 alloy or similar to that of AA2195 alloy, but with lower mechanical properties.

[0017] The 4XXX series alloys have been considered for aerospace applications. WO 95 / 34691 relates to an aluminum alloy sheet intended for mechanical, aeronautical, or space-related construction, characterized by the following composition (% by weight): Si 6.5–11%, Mg 0.5–1.0%, Cu < 0.8%, Fe < 0.3%, Mn < 0.5%, and / or Cr < 0.5%, Sr 0.008–0.025%, Ti < 0.02%, total other elements < 0.2%, remainder aluminum. Sheets according to this patent application exhibit a high modulus of elasticity and low density and can be used particularly for wing undersides and aircraft fuselage skinning, as well as for cryogenic rocket tanks.

[0018] Today, hydrogen is being considered for civil aviation applications. Hydrogen is presented as the most suitable "clean" fuel for the aviation of tomorrow. However, its storage in an aircraft remains an unresolved issue. It is likely that a complete redesign of aircraft will be necessary, as their fuel is currently stored in the wings. Storing hydrogen in liquid form requires a temperature of -253°C. The European CRYOPLANE project (Report 24 / 09 / 2003 - contract no. G4RD-CT-2000-00192) proposes, for example, using several cryogenic tanks arranged, for instance, around the fuselage.

[0019] While there are synergies between spaceflight and civil aviation, there are also significant differences in terms of specifications. For space applications, tanks are either non-reusable or reusable only a limited number of times. For civil applications, density is a critical issue because fuel consumption is highly dependent on the structure's weight. In commercial aviation, the focus is on improving hydrogen storage systems in terms of weight, cost, and safety. Safety requirements for civil aviation differ from those for space launch vehicles, as hydrogen storage tanks for commercial aircraft must withstand tens of thousands of takeoffs and landings and maintain hydrogen in a liquid state for much longer periods.

[0020] Cryogenic tanks for the storage of cryogenic liquids in civil aviation therefore require that the constituent material have good toughness, as well as sufficient strength, low density, low coefficient of thermal expansion, and high rigidity.

[0021] The present invention was developed to reduce the weight of tanks, particularly storage tanks containing cryogenic liquids, especially liquid hydrogen, in civil aviation, by proposing a material with sufficient damage tolerance combined with adequate mechanical strength, a low coefficient of thermal expansion, and a high modulus of elasticity. This solution ensures good functional performance while simultaneously offering optimized mass, operational durability, and reduced dimensional changes during temperature cycling.

[0022] Description of the invention

[0023] A first object of the invention relates to a method for manufacturing a rolled product of aluminum alloy 4000 comprising the following steps: a) Casting of an aluminum alloy plate comprising, in weight percentage: Si 11.5 - 12.5

[0024] Fe < 0.6

[0025] Cu 0.1 - 1.0 Mn < 0.3

[0026] Mg 0.3 - 1.0

[0027] Ti 0 - 0.15

[0028] Sr 0.01 - 0.05 other elements and impurities < 0.05 each, total < 0.15, remainder aluminum, b) Homogenization and / or heating of the plate at a temperature of 400 to 560 °C, c) Hot rolling of the homogenized and / or heated plate, optionally followed by cold rolling to obtain a rolled product of thickness of 0.8 to 12.5 mm, d) Solutioning of the rolled product at a temperature of 520 °C to 555 °C, followed by cooling at a rate of at least 1 °C / s in the temperature range of 450 °C to 250 °C, e) Tempering of the solution-treated and quenched rolled product at a temperature of 160 °C to 180 °C for a period of 3 h to 24 h.

[0029] Preferably, the Cu content is 0.10 to 0.50% by weight and even more preferably 0.20 to 0.50% by weight.

[0030] Preferably, the income generated in step e) comprises a sequence whose temperature, expressed in °C, is described by a function T° c (t) depending on the time t such that the maximum temperature reached T max is between 160 °C and 180 °C and the duration of maintenance at a temperature between 160 °C and 180 °C is such that the equivalent duration calculated at a temperature of 175 °C is between 3 a.m. and 8 a.m., where tH c -4 5 ° is calculated according to the formula:

[0031] 136000 / 1 1 Y feQ 5 ° C = I dt. exp

[0032] 8,314 ' \T° c (t) + 273 " 175 + 273 /

[0033] Preferably, the income includes a single tier.

[0034] The rolled product obtained by the process of the invention has a yield strength in the transverse direction of rolling R P o.2(TL) of at least 280 MPa, and a value of K app(TL) of at least 35 MPaYm, where the yield strength is measured according to ASTM E8 and the value of K app is measured according to ASTM E561-2022 with a CCT specimen of width W=406 mm and thickness B=3mm.

[0035] Preferably, the rolled product has a yield strength in the transverse rolling direction of 280 MPa to 320 MPa and a K value app (TL) of 35 to 50 MPaYm. Preferably, the rolled product obtained by the process of the invention exhibits a distributed elongation A g % in the cross-roll direction according to ASTM E8 greater than 5.5%, preferably 6.5%.

[0036] The rolled product in aluminum alloy 4000 is preferably used for the manufacture of tanks, preferably an aircraft hydrogen storage tank.

[0037] Another object of the invention relates to a method for manufacturing a tank, preferably a cryogenic liquid storage tank, comprising successive steps, a first step of manufacturing a rolled product with a thickness of 0.8 to 12.5 mm according to the first object of the invention, and a second step of shaping said rolled product to form a side wall of the tank. Preferably, the shaping is done by rolling.

[0038] Detailed description of the invention

[0039] The invention relates to a method for manufacturing a rolled product of aluminum alloy 4000, preferably used for manufacturing tanks. In a preferred embodiment, the tank is a storage tank for cryogenic liquids intended for civil aviation. In accordance with the guidelines of the Aluminum Association (Washington DC 2006, USA), aluminum alloys are designated using a four-digit numerical system. The first digit indicates the principal alloying element: for 4000 alloys, "4" signifies that the principal element is silicon.

[0040] All aluminum alloys mentioned below are designated according to the rules and designations defined by The Aluminum Association in the Registration Record Series that it publishes regularly, unless otherwise stated.

[0041] The metallurgical states referred to are designated according to the European standard EN-515 (1993) unless otherwise stated.

[0042] All alloy compositions are provided as % by weight (% by weight).

[0043] Unless otherwise stated, the static mechanical characteristics, in other words the breaking strength R m , the tensile yield strength R p The elongation at break (A%) is determined by a tensile test according to ASTM E8 (2024 version). For the intended use, the uniformly distributed elongation, denoted A, is used. g The %, (uniform deformation according to Anglo-Saxon terminology) is interesting to consider as it reflects the formability of the rolled product. The sampling and direction of the test are defined by standard EN 485-1.

[0044] Young's modulus is measured according to ASTM 1876. The stress intensity factor and crack extension values ​​are effective values ​​as defined in ASTM E561-2022. The critical stress intensity factor Kc, in other words, the intensity factor that makes the crack unstable, is calculated from the R curve. The stress intensity factor Kco is also calculated by assigning the initial crack length at the start of monotonic loading to the critical load. Both of these values ​​are calculated for a specimen of the required shape. app represents the Kco factor corresponding to the specimen that was used to perform the R curve test.

[0045] Unless otherwise stated, the definitions in standard EN 12258 apply.

[0046] Unexpectedly, the inventors found it advantageous to use a rolled aluminum alloy product from the 4XXX series with a thickness of 0.8 mm to 12.5 mm for manufacturing tanks with a composition by weight of: Si 11.5 - 12.5

[0047] Fe < 0.6

[0048] Cu 0.1 - 1.0

[0049] Mn < 0.3

[0050] Mg 0.3 - 1.0

[0051] Ti 0 - 0.15

[0052] Sr 0.01 - 0.05 other elements and impurities < 0.05 each, total < 0.15, remainder aluminium.

[0053] The inventors found that by choosing such a composition, combined with suitable processing parameters, it is possible to obtain a rolled product exhibiting a yield strength in the TL R direction p o.2 (TL) measured according to ASTM E8 of at least 280 MPa, and a K value app(TL) measured according to ASTM E561-2022 with a specimen of width W=406 mm and thickness B = 3 mm of at least 35 MPa^ / m.

[0054] The silicon content is at least 11.5%, so that the alloy density is minimized. The density of the rolled product depends on the composition, particularly the Si and Mg content. Typically, the density of the rolled product is between 2.63 and 2.66. A Si content exceeding 12.5% ​​is detrimental to damage tolerance and formability.

[0055] The magnesium content is between 0.3 and 1.0% by weight. A content below 0.3% does not allow for sufficient mechanical properties. The magnesium content is preferably no more than 0.8% by weight, and preferably no more than 0.7% by weight, in order to improve formability while obtaining sufficient mechanical strength.

[0056] The copper content is from 0.1% to 1.0%. Preferably, the copper content is from 0.10% to 0.50% by weight. The copper content is at least 0.1%, preferably 0.10%, preferably 0.20%, or even 0.30% to obtain high mechanical strength after tempering. The copper content is preferably a maximum of 0.50% for corrosion resistance.

[0057] The manganese content is preferably a maximum of 0.3% by weight. A manganese content exceeding 0.3% by weight can negatively impact formability. In one embodiment, it is advantageous for the manganese content to be less than 0.15% by weight, or even 0.10% by weight, or even 0.05% by weight.

[0058] The strontium content ranges from 0.01 to 0.05% by weight. Strontium allows for control of the size of silicon-containing eutectic compounds during solidification and / or modification of their structure, which has a favorable impact on mechanical properties, particularly formability.

[0059] The titanium content is between 0 and 0.15% by weight. Advantageously, an amount of titanium of between 0.01 and 0.15% by weight is added.

[0060] It is preferable to limit the content of unavoidable impurities in the alloy to achieve the most favorable damage-tolerance properties. The iron content should be a maximum of 0.6% by weight, preferably less than or equal to 0.5%, or even 0.3%. An iron content exceeding 0.6% by weight can negatively affect formability and toughness.

[0061] The other impurities have a content of less than or equal to 0.05% by weight each and 0.15% by weight in total. The remainder is aluminum.

[0062] Such a 4XXX alloy has the advantage of a lower density than alloys traditionally used for cryogenic tanks, such as AA2219 or AA2195. Furthermore, in addition to its lower density of 2.63 to 2.66, it offers the advantage of a higher Young's modulus, which is beneficial for structural rigidity, and a lower coefficient of thermal expansion (also known as the thermal expansion coefficient), which is beneficial for structural compatibility during temperature cycling, particularly between cryogenic and ambient temperatures. Typical values ​​for density, Young's modulus, and coefficient of expansion for the alloy according to the invention with conventional alloys are compared in Table 1 below.

[0063] [Table 1]

[0064] The manufacturing process for the laminated product according to the invention comprises the following successive steps.

[0065] First, the manufacture of a foundry plate whose composition in % by weight is: Si 11.5 - 12.5

[0066] Fe < 0.6

[0067] Cu 0.1 - 1.0

[0068] Mn < 0.3

[0069] Mg 0.3 - 1.0

[0070] Ti 0 - 0.15

[0071] Sr 0.01 - 0.05 other elements and impurities < 0.05 each, total < 0.15, remainder aluminium.

[0072] Preferably this alloy contains aluminum alloy scraps or waste.

[0073] Aluminum alloy scrap refers to products made of aluminum and / or aluminum alloys resulting from the collection and / or recovery of metals produced at various stages of manufacturing; this is called production scrap, or of products after use, called recovery scrap. Examples of production scrap include foundry dross, drips, shredded scrap, and turnings as defined by EN 12258-3. Examples of recovery scrap include scrap or waste from end-of-life vehicles.

[0074] Preferably, the 4XXX series alloy contains at least 50% by weight of aluminum alloy scrap or waste; more preferably, at least 80% by weight. Preferably, the 4XXX series alloy contains at least 50% by weight of recycled scrap; more preferably, at least 80% by weight of recycled scrap.

[0075] Preferably, the salvage scrap is scrap or waste from out-of-service vehicles, preferably at least 50%, plus preferably at least 80%.

[0076] The chosen composition of the rolled product according to the invention is particularly interesting because end-of-life vehicles, such as, but not limited to, passenger cars, light vehicles, vans, and trucks, typically contain numerous aluminum parts. Some of these end-of-life vehicles are defined by Directive 2000 / 53 / EC. These aluminum parts are very diverse. They can include components such as heat exchangers like air conditioning condensers and evaporators, engine cooling or cabin heating radiators, charge air coolers, oil coolers and radiators, and fuel coolers. They can also include engine parts such as cylinder heads, cylinder blocks, or engine blocks. Other castings, for example, chassis components, can also be included. These parts contain silicon-filled alloys.

[0077] The rolled product according to the invention can be used to create a recycling stream for end-of-life vehicles. The 4xxx alloy of the rolled product according to the invention preferably contains aluminum alloy scraps or waste, preferably scraps or waste from vehicles in use, preferably at least 50%, and more preferably at least 80%.

[0078] Preferably, the casting of the slab is carried out by semi-continuous vertical casting. Preferably, the slab is then scalped to remove the cortical layer.

[0079] The foundry plate is then homogenized preferably at a temperature of 400 to 560 °C, preferably for at least 1 hour, preferably at a temperature of at least 480 °C for at least 3 hours.

[0080] The cast plate is then rolled to a thickness of 0.8 mm to 12.5 mm, preferably 2 mm to 8 mm. It is first hot-rolled to a preferred thickness of 4 mm to 12.5 mm. In a preferred embodiment for achieving thinner thicknesses, cold rolling may be carried out with a preferred reduction ratio of at least 50% to obtain a thickness of 0.8 mm to 5 mm; preferably, the final thickness after cold rolling is 0.8 mm to 4 mm. In one embodiment, the cold rolling is carried out in two stages separated by annealing to prevent the formation of edge cracks that could lead to breakage of the thin sheet.

[0081] The rolled product is then solution-treated and quenched. Solution treatment is carried out at a temperature of 520 °C to 555 °C, preferably at least 540 °C, for at least 30 seconds, preferably at least 1 minute. Quenching takes place in air or water at a rate of at least 1 °C / s, preferably 5 °C / s, within a temperature range of 450 °C to 250 °C.

[0082] In one embodiment, the rolled product can be wound at a temperature of 50 to 100 °C, preferably 60 to 80 °C, then the coil cools naturally to ambient temperature, typically between 10 °C and 35 °C.

[0083] In a preferred embodiment, the rolled product undergoes a planing step after quenching.

[0084] The hardened, rolled product, optionally planed and / or coiled, then undergoes tempering at a temperature of 160°C to 180°C for a period of 3 to 24 hours. The tempering conditions—temperature and duration—are chosen to achieve a yield strength in the TL, R direction. p o.2 (TL), measured according to ASTM E8 of at least 280 MPa, and a Kapp (TL) value of at least 35 MPaYm, measured according to ASTM E561-2022 with a specimen of width W=406 mm and thickness B = 3mm.

[0085] A tempering temperature above 180 °C does not allow for sufficient formability, as well as the expected level of toughness of at least 35 MPaYm.

[0086] Preferably, the income includes a sequence whose temperature, expressed in °C, is described by a function T° c (t) depending on time t, such that the maximum temperature reached T maxis between 160 °C and 180 °C and the holding time at a temperature between 160 °C and 180 °C is such that the equivalent time tgq 5 ° calculated at a temperature of 175 °C is between 3 h and 8 h, where tH c -4 5 ° is calculated according to the formula:

[0087] 136000 1 1 Y teq 5 ° C = j dt. ex P

[0088] 8,314 ' (t) + 273 " 175 + 273 /

[0089] Preferably, the quenched rolled product, optionally planed and / or coiled, undergoes a tempering process comprising a single stage from 160 °C to 180 °C for a duration of 3 h to 24 h. After tempering, the rolled product exhibits a yield strength in the TL direction, Rpo.2 (TL), measured according to ASTM E8, of at least 280 MPa, preferably from 280 MPa to 320 MPa.

[0090] After heating, the rolled product has a value of K app(TL) of at least 35 MPa^ / m, preferably between 35 and 50 MPa^ / m. measured according to ASTM E561-2022 with a specimen of width W=406 mm and thickness B of 3 mm.

[0091] Preferably, the rolled product has a distributed elongation (Ag%) in the TL direction, measured according to ASTM E8, greater than 5.5%, preferably 6.5%, to facilitate forming. Preferably, the distributed elongation (Ag%) in the TL direction is less than or equal to 7.5% to maintain a Kapp (TL) value of 35 to 50 MPa / m.

[0092] After tempering, the rolled product is shaped for tank manufacturing, preferably for storing cryogenic liquids. Cryogenic tanks are airtight, vacuum-insulated containers that allow for the safe and efficient storage of cryogenic liquids, such as hydrogen. They are preferably cylindrical in shape.

[0093] The tank is generally manufactured from rolled products that are shaped, preferably by rolling, to form the cylindrical shape which is then assembled with domes. This shaping, preferably by rolling, produces a cylindrical shape that forms the side walls of the tank. These walls can be welded together. One advantage of the alloy of the invention is that it can be welded using a fusion process such as TIG welding, which facilitates the industrialization of such manufacturing. Depending on the size of the tank, several rolled products can be used to create the cylindrical shape. The cylindrical shape is then assembled with the domes to obtain a hermetically sealed tank. The rolled product according to the invention can also be used to form the domes. The dome can be made in one piece by spinning (also called metal spin forming in English). It can also be made up of several segments.

[0094] It is particularly advantageous to be able to shape the rolled product in its tempered state without needing to perform additional tempering after shaping. This allows for a simple and economical process.

[0095] Example 1

[0096] Two 560 mm thick plates were cast. Their composition according to the invention is shown in Table 2 below. [Table 2] - Composition by weight %

[0097] The plates were heated to 500 °C for over 4 hours, then hot-rolled to a thickness of 7.3 mm and subsequently cold-rolled to a thickness of 3 mm with an intermediate annealing. The resulting thin sheets were solution-treated at 540 °C for a holding time of approximately 70 seconds, and then quenched. The sheets were then aged at room temperature for one month to achieve a T4 condition, and each underwent a single-step tempering as described in Table 2.

[0098] The sheets were then characterized in tension according to the recommendations of ASTM E8 in the direction perpendicular to the rolling direction, denoted TL. The value of the apparent stress intensity factor at break K app expressed in MPa^ / m, defined according to the ASTM E561-2022 standard was measured in the TL direction on CCT specimens of width 406 mm and thickness 3 mm (see Table 3).

[0099] [Table 3] - Measured mechanical properties and toughness.

[0100] (*) Kapp value not measured but estimated based on measured static properties.

[0101] It is observed that the product tempered at a temperature above 200 °C (2R) exhibits a distributed elongation (Ag%) of less than 5.5% and a lower estimated Kapp value. The inventors believe this is a major obstacle to achieving a Kapp toughness (TL) of at least 35 MPa^ / m.

Claims

DEMANDS 1. Method for manufacturing a rolled product of aluminum alloy 4000 comprising the following steps: a) Casting of an aluminum alloy plate comprising, by weight percentage, Si 11.5 - 12.5 Fe < 0.6 Cu 0.1 - 1.0 Mn < 0.3 Mg 0.3 - 1.0 Ti 0 - 0.15 Sr 0.01 - 0.05 other elements and impurities < 0.05 each, total < 0.15, remainder aluminum, b) Homogenization and / or heating of the plate at a temperature of 400 to 560 °C, c) Hot rolling of the homogenized and / or heated plate, optionally followed by cold rolling to obtain a rolled product of thickness of 0.8 to 12.5 mm, d) Solutioning of the rolled product at a temperature of 520 °C to 555 °C, followed by cooling at a rate of at least 1 °C / s in the temperature range of 450 °C to 250 °C, e) Tempering of the solution-treated and quenched rolled product at a temperature of 160 °C to 180 °C for a period of 3 h to 24 h.

2. Manufacturing method according to claim 1 wherein the Cu content is 0.10 to 0.50% by weight, preferably 0.20 to 0.50% by weight.

3. A manufacturing method according to claim 1 or 2, wherein the tempered rolled product exhibits a yield strength in the transverse direction of rolling R P o.2(TL) of at least 280 MPa, and a value of K app (TL) of at least 35 MPa^ / m, where the yield strength is measured according to ASTM E8 and the value of K app is measured according to ASTM E561-2022 with a CCT specimen of width W=406 mm and thickness B=3mm.

4. A manufacturing method according to any one of claims 1 to 3, wherein the rolled product has a yield strength in the transverse rolling direction of 280 MPa to 320 MPa and a K value app (TL) of 35 to 50 MPax / m.

5. A manufacturing method according to any one of claims 1 to 4 such that the rolled product exhibits a distributed elongation A g % in the cross direction of rolling TL according to ASTM E8 greater than 5.5%, preferably 6.5%.

6. A manufacturing method according to any one of claims 1 to 5, wherein the tempering comprises a sequence whose temperature, expressed in °C, is described by a function T° c (t) depending on time t, such that the maximum temperature reached T max is between 160 °C and 180 °C and the holding time at a temperature between 160 °C and 180 °C is such that the equivalent time tgq 5 ° calculated at a temperature of 175 °C is between 3 a.m. and 8 a.m., where tH 5 ° is calculated according to the formula:

7. Manufacturing method according to any one of claims 1 to 6 such that the income comprises a single step.

8. Method of manufacturing a tank, comprising as successive steps, a first step of manufacturing a rolled product of thickness from 0.8 mm to 12.5 mm obtained according to one of claims 1 to 7, and a second step of shaping said rolled product to form a side wall of the tank, preferably the shaping is done by rolling.

9. Use of a rolled product of aluminium alloy 4000 obtained according to any one of claims 1 to 7 for the manufacture of a tank, preferably a hydrogen storage tank for an aircraft.

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